Balanced brake assembly having coincident piston application

ABSTRACT

A brake assembly ( 30 ) has a plurality of brake fluid actuated pistons. The brake assembly includes a brake inlet port ( 46 ) for receiving brake fluid from a fluid reservoir. The brake assembly includes a plurality of cylinders ( 32, 34, 36, 38, 40, 42 , and  44 ) for actuating a corresponding plurality of pistons. The plurality of cylinders includes at least a first cylinder ( 32 ), a second cylinder ( 44 ), and a third cylinder ( 38 ) for actuating corresponding pistons. The first, second, and third pistons actuate at first, second, and third time intervals. A fluid distribution manifold ( 48 ) is connected in fluid communication with the brake inlet port. A plurality of cylinder manifolds ( 50 ) includes at least a first cylinder manifold connected in fluid communication with the fluid distribution manifold and the first cylinder, a second cylinder manifold connected in fluid communication with the fluid distribution manifold and the second cylinder, and a third cylinder manifold connected in fluid communication with the fluid distribution manifold and the third cylinder. The first, second, and third cylinder manifolds connect the first, second, and third cylinders in parallel fluid flow, and the parallel fluid flow tends to equalize the first, second, and third time intervals.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. patent applicationSer. No. 09/388,245, filed Sep. 1, 1999, abandoned as of the filing dateof this application, which was a continuation of prior U.S. patentapplication Ser. No. 08/731,763, filed Oct. 18, 1996, now U.S. Pat. No.5,971,111.

FIELD OF THE INVENTION

The present invention relates to a brake assembly, and more particularlyto a balanced aircraft brake assembly having coincident pistonapplication.

BACKGROUND OF THE INVENTION

Airplane brake assemblies are well known in the art. FIG. 1 shows atypical prior art brake assembly 2. The brake assembly 2 includes abrake inlet port 4. The brake inlet port 4 is typically located at thetop of the brake assembly 2 for purging air bubbles that may be presentin brake assembly hydraulic fluid. The brake assembly 2 further includesa plurality of piston and cylinder assemblies 6, a pressure plate 8, aplurality of rotor and stator assemblies 10, and a torque tube 12. Ascan be seen in FIG. 1, the piston and cylinder assemblies 6 are locatedin a substantially circular arrangement about the brake assembly 2 forproviding an even pressure distribution about the pressure plate 8.

FIG. 2 shows a schematic diagram of a typical brake assembly, such asthe brake assembly 2 of FIG. 1. The brake inlet port 4 is shown at thetop of the brake assembly 2. However, it is well known in the art tolocate the inlet port at any position on the brake assembly. The brakeinlet port 4 is coupled to a header from a hydraulic fluid reservoir(not shown). The cylinders 14, 16, 18, 19, 20, 22, and 24 are connectedin series fluid communication via hydraulic manifold sections 26. Thecylinders 14 and 24 are also coupled to the brake inlet port 4 viamanifold sections 26. Flow restrictors 28 may be included in each of themanifold sections 26.

When a pilot applies an aircraft's brakes, hydraulic fluid flows fromthe hydraulic reservoir (not shown) through the header to the brakeinlet port 4. When hydraulic fluid is introduced to the brake inlet port4, hydraulic fluid first flows to the cylinders 14 and 24 that arecoupled to the brake inlet port 4. Hydraulic fluid pressure increaseswithin the cylinders 14 and 24 as they fill. When the pressure in thecylinders 14 and 24 reaches a predetermined threshold, their associatedpistons actuate and press against the pressure plate 8, which clamps therotor and stator assemblies 10 against the torque tube 12. After thecylinders 14 and 24 have filled, hydraulic fluid next flows through themanifold sections 26 to the cylinders 16 and 22. The cylinders 16 and 22fill with hydraulic fluid and, in turn, hydraulic fluid flows throughthe manifold sections 26 to the cylinders 18 and 20. Finally, afterflowing through the above-identified series of cylinders, hydraulicfluid flows to and fills the cylinder 19. Thus, the pistons associatedwith the cylinders 14, 16, 22, and 24, located toward the brake inlet 4at the top of the brake assembly 2, actuate and clamp the rotor andstator assemblies 10 against the torque tube 12 before the pistonsassociated with the cylinders 18, 19, and 20, located toward the bottomof the brake assembly 2 away from the brake inlet port 4, actuate andclamp against the torque tube 12.

As a result, the rotor and stator assemblies 10 near the brake inletport 4 at the top of the brake assembly 2 are compressed before therotor and stator assemblies 10 farther away from the brake inlet port 4at the bottom of the brake assembly 2. In some known brake assemblies,the time delay between actuation of piston and cylinder assemblieslocated closer to the brake inlet port and actuation of piston andcylinder assemblies located farther away from the brake inlet port hasbeen recorded in excess of 50 ms. This time delay causes the torque tube12 to react through the rotor and stator assemblies 10 at the top of thebrake assembly 2 against the piston and cylinder assemblies 6 at the topof the brake assembly 2 while the piston and cylinder assemblies 6 atthe bottom of the brake assembly 2 are still compressing against thetorque tube 12. This results in a lateral displacement between the topand bottom regions of the rotor and stator assemblies 10 and the torquetube 12. When the piston and cylinder assemblies 6 at the bottom of thebrake assembly 2 actuate, the bottom of the torque tube 12 reactsthrough the bottom region of the rotor and stator assemblies 10 againstthe piston and cylinder assemblies 6 at the top of the brake assembly 2.This, in combination with a return force from the top region of thetorque tube 12 causes the clamping force at the top region of the brakeassembly 2 to decrease relative to the clamping force at the bottom ofthe brake assembly 2. When the asymmetric clamping cycle andcorresponding lateral displacement repeats for a rotating wheel, avibration of the brake results. The vibration is known as “brake whirl”or “brake wheel vibration.”

An imbalance in piston pressure exists across the brake assembly 2during the time that the pistons are actuating. Piston pressures andtorque tube clamping forces are not equalized across the brake assembly2 during pressure transitions. Each piston actuates as an individualdynamic element within the brake assembly 2, rather than all the brakepistons actuating together as a single element. The resultingdifferential pressure between the pistons during braking undesirablyreduces overall brake system stiffness.

The asymmetric clamping cycle described above can also cause stators todevelop a tapered wear pattern. Further, the time delay betweenactuation of top and bottom region pistons degrades the frequencyresponse of the brake assembly 2. Because the frequency response of thebrake assembly 2 is lower than the frequency response of autobrake andantiskid valves included in aircraft brake systems, degradation in thebrake assembly frequency response degrades frequency response of theoverall braking system.

It would therefore be desirable to minimize time delays betweenactuation of brake pistons in order to minimize asymmetric clamping.Many prior art brake assemblies 2 include the flow restrictors 28 in themanifold sections 26 in an attempt to reduce brake wheel vibration orbrake whirl. As can be appreciated, the flow restrictors 28 insteadserve to further increase the time delay between actuation of brakepistons. Therefore, the flow restrictors 28 make brake clamping evenmore asymmetric and worsen the problems of brake whirl, uneven statorwear, and degraded frequency response. There is thus an unmet need inthe art to minimize asymmetric brake clamping.

SUMMARY OF THE INVENTION

A brake assembly constructed in accordance with the present inventionincludes a plurality of brake fluid actuated pistons. The brake assemblyincludes a brake inlet port for receiving brake fluid from a fluidreservoir. A plurality of cylinders actuates a corresponding pluralityof pistons, and includes at least a first cylinder, a second cylinder,and a third cylinder for actuating corresponding pistons. A fluiddistribution manifold is connected in fluid flow communication with thebrake inlet port and the first, second, and third cylinders. The fluiddistribution manifold connects the first, second, and third cylinders inparallel fluid flow.

The balanced brake assembly of the present invention actuates brakepistons at substantially the same time and minimizes asymmetric brakeclamping. Thus, the problems of brake whirl, uneven stator wearpatterns, and degraded brake assembly frequency response are minimized.

In one embodiment of the present invention, first, second, and thirdmanifold sections couple the first, second, and third cylinders inparallel fluid communication with the fluid distribution manifold. In afurther aspect of the present invention, the first and second manifoldsections include first and second flow restrictors.

In an alternate embodiment, a brake assembly has a plurality of brakefluid actuated pistons. The brake assembly includes a plurality ofcylinders for actuating a corresponding plurality of pistons, includingat least a first cylinder, a second cylinder, and a third cylinder foractuating corresponding pistons. A brake inlet port receives brake fluidfrom a fluid reservoir, and is disposed equidistant from each of thecylinders. The brake assembly includes a plurality of manifolds. Each ofthe manifolds couples the brake inlet port to an associated cylinder andhas an equalized length and an equalized volume such that each of thecylinders actuates its corresponding piston at an equalized timeinterval.

According to a further aspect, the plurality of manifolds is disposedradially from the brake inlet port.

In another alternate embodiment, the brake assembly has a plurality ofbrake fluid actuated pistons. The brake assembly includes a brake inletport for receiving brake fluid from a fluid reservoir. A fluiddistribution manifold is connected in fluid communication with the brakeinlet port. A first cylinder is provided for actuating a first brakepiston. The first cylinder is connected in fluid communication to afirst supply segment of the fluid distribution manifold to define afirst fluid path distance from the brake inlet port. A second cylinderis provided for actuating a second brake piston. The second cylinder isconnected in fluid communication to a second supply segment of the fluiddistribution manifold to define a second fluid path distance from thebrake inlet port that is greater than the first fluid path distance. Thefluid distribution manifold includes a distribution segment coupling thefirst and second supply segments of the fluid distribution manifold toequalize the supply of brake fluid to the first and second cylinders.

In a further aspect, the distribution segment couples the first andsecond cylinders in parallel fluid communication.

In an even further aspect, the distribution segment couples the firstand second cylinders in series fluid communication, and the first andsecond supply segments couple the first and second cylinders in parallelfluid communication.

The present invention provides a method of concurrently actuating aplurality of brake fluid actuated pistons of a brake assembly. The brakeassembly has a brake inlet port. The brake assembly includes at least afirst cylinder for actuating a first piston, a second cylinder foractuating a second piston, and a third cylinder for actuating a thirdpiston. The first cylinder is coupled in fluid communication with thebrake inlet port through a first fluid flow path, the second cylinder iscoupled in fluid communication with the brake inlet port through asecond fluid flow path, and the third cylinder is coupled in fluidcommunication with the brake inlet port through a third fluid flow path.Brake fluid is applied to the brake inlet port. Brake fluid is suppliedfrom the brake inlet port to the first brake cylinder for actuating thefirst brake piston and to the second brake cylinder for actuating thesecond brake piston. Brake fluid is concurrently supplied from the brakeinlet port to the third brake cylinder in parallel fluid communicationwith the brake fluid supplied to the first and second cylinders, suchthat the first, second, and third brake pistons actuate at an equalizedtime interval.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thisinvention will become better understood by reference to the followingdetailed description, when taken in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is a perspective of a prior art brake assembly with a quartersection cut away;

FIG. 2 is a schematic diagram of a typical prior art brake assembly;

FIG. 3 is a schematic diagram of a brake assembly according to a firstembodiment of the present invention;

FIG. 4 is a cross-sectional schematic view of a flow restrictor disposedwithin a manifold branch that supplies hydraulic brake fluid to acylinder, an end portion of which is shown, for the embodiment of thepresent invention shown in FIG. 3;

FIG. 5 is a schematic diagram of a brake assembly according to anotherembodiment of the present invention; and

FIGS. 6A-6D are corresponding schematic diagrams of other embodiments ofa brake assembly of the present invention, utilizing both parallel andseries interconnection of brake cylinders.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 3 shows a schematic diagram of a brake assembly 30 according to afirst embodiment of the present invention. The brake assembly 30includes cylinders 32, 34, 36, 38, 40, 42, and 44. The brake assembly 30includes a brake inlet port 46. The brake inlet port 46 is suitablylocated at the top of the brake assembly 30 for purging air bubbles thatmay be present in brake assembly hydraulic fluid. However, the locationof a brake inlet port 46 at other than the top of the brake assembly 30is also acceptable, as is known in the art. The brake inlet port 46 iscoupled to a brake system header (not shown) for receiving brakehydraulic fluid for distribution to the plurality of brake cylinders.The brake assembly 30 also includes pistons (not shown), a pressureplate (not shown), rotor and stator assemblies (not shown) and a torquetube (not shown), configured similarly to those components ofconventional brake assemblies, such as the previously described brakeassembly 2 shown in FIG. 1. However, the routing of hydraulic brakefluid to the cylinders of the brake assembly 30 of the present inventionis distinct from that previously described.

In the brake assembly 30, a parallel distribution manifold 48 is coupledto the brake inlet port 46 and to each of the cylinders 32, 34, 36, 38,40, 42, and 44. The parallel distribution manifold 48 may be asubstantially circular manifold. In such an embodiment, the shape of theparallel distribution manifold 48 corresponds to the arrangement of theplurality of pistons and cylinders about the brake assembly 30. Manifoldsections 50 couple the parallel distribution manifold 48 to each of thecylinders of the brake assembly 30. An individual manifold section 50branches radially off of the parallel distribution manifold 48 to supplyhydraulic brake fluid to a corresponding cylinder. It is desirable thatthe manifold sections 50 be as straight and short as practicable inorder to minimize hydraulic losses and reduce time delays in fillingcylinders with hydraulic fluid.

In a further aspect of the brake assembly 30, a flow restrictor 52 maybe included in each of the manifold sections 50 coupled to correspondingcylinders 32, 34, 36, 40, 42, and 44, as indicated in FIG. 3. FIG. 4shows a pictorial view of one embodiment of a flow restrictor 52 mountedwithin a manifold section 50, which supplies fluid to a representativecylinder 53 and piston 55. As seen in FIG. 4, the flow restrictor 52 maybe configured as a restrictor check valve. The flow restrictor 52includes a cylindrical body 54, which is preferably located at the topof its associated cylinder and is oriented upwardly from horizontal forpurging any air bubbles that may be present in the brake hydraulicfluid. The body 54 of the flow restrictor 52 includes a first orifice 56in the end of the restrictor 52 that is in closest proximity to themanifold section 50. The flow restrictor 52 includes a floatingrestrictor piston 58 that includes a second orifice 60 that is smallerthan the first orifice 56. The flow restrictor 52 also includes alow-force return spring 62 that biases the floating piston 58 intosealing engagement with an outlet port 63 of the body 54.

When a cylinder with one of the flow restrictors 52 fills, therestrictor piston 58 is held in sealing engagement against outlet port63 by hydraulic pressure from the manifold 48 and return spring force,and fluid flows through the second orifice 60 in restrictor piston 58 toits associated cylinder. When brake application has ended, hydraulicpressure within the cylinder causes the restrictor piston 58 to move outof engagement with the outlet port 63 such that the restrictor checkvalve 54 is held open until differential pressure between the firstorifice 56 and the outlet port 63 is less than the return spring 62force. This provides an outlet port that is large enough so air canreadily escape.

When the brakes are applied in an aircraft utilizing the brake assembly30, hydraulic fluid is supplied to the brake inlet port 46, as shown inFIG. 3. Hydraulic fluid flows from the brake inlet port 46 to theparallel distribution manifold 48. Hydraulic fluid flows in parallelfluid communication from the parallel distribution manifold 48 throughthe manifold sections 50 to each of the cylinders 32, 34, 36, 38, 40,42, and 44. Each of the cylinders of the brake assembly 30 fills atsubstantially the same time, and the pistons of the brake assembly 30thus actuate substantially simultaneously.

It will be appreciated that actuating the various brake pistonssubstantially simultaneously represents a significant improvement overbrake assemblies previously known in the art, such as that illustratedin FIGS. 1 and 2. In the present invention, any time differences infilling the cylinders of the brake assembly 30 are due to some cylindersbeing located farther away from the brake inlet port 46 than othercylinders. For example, the cylinders 34 and 42 are coupled to theparallel distribution manifold 48 slightly farther away from the brakeinlet port 46 than are the cylinders 32 and 44. Likewise, the cylinders36 and 40 are coupled to the parallel distribution manifold 48downstream of the cylinders 34 and 42. Finally, the cylinder 38 iscoupled to the parallel distribution manifold 48 downstream of thecylinders 36 and 40. The cylinders 32 and 44 may fill with hydraulicfluid shortly before the cylinders 34 and 42 fill. Likewise, thecylinders 36 and 40 may fill just after the cylinders 34 and 42 fill.Finally, the cylinder 38 may fill shortly after the cylinders 36 and 40fill. However, it will be appreciated that any such time delay isnegligible compared to the substantial time delays between pistonactuation in series-configured brake assemblies previously known in theart.

The use of flow restrictors 52, such as those illustrated in FIGS. 3 and4, further minimizes any time delay between the filling of each of thecylinders. As described above, the cylinder 38 fills last because it isfarthest from the brake inlet port 46. Therefore, further restrictingthe flow of hydraulic fluid to the cylinder 38 by including a flowrestrictor in the manifold section 50 coupled to the cylinder 38 is notdesirable. The flow restrictors 52 associated with the cylinders 32 and44 have orifices of a first predetermined diameter to insert a firsttime delay such that the cylinders 32 and 44 fill at substantially thesame time that the cylinder 38 fills. Likewise, the flow restrictors 52associated with the cylinders 34 and 42 have orifices of a secondpredetermined diameter, greater than the first predetermined diameter,to insert a second time delay, shorter than the first time delay, suchthat the cylinders 34 and 42 fill at substantially the same time as thecylinder 38. Finally, the flow restrictors 52 associated with thecylinders 36 and 40 have a still greater third predetermined diameter toinsert a third time delay, shorter than the second time delay, such thatthe cylinders 36 and 40 fill at substantially the same time as thecylinder 38. Thus, it is preferred that flow restrictors 52 be includedin the brake assembly 30. However, a brake assembly 30 that does notinclude flow restrictors 52 presents a major improvement in reducingcylinder actuation time delays.

FIG. 5 shows a schematic diagram of a second embodiment of a brakeassembly 70 of the present invention. The brake assembly 70 includescylinders 72, 74, 76, 78, 80, 82, and 84. Each of the cylinders shown inFIG. 5 is associated with a brake piston (not shown) for pressingagainst a pressure plate (not shown) and clamping brake rotor and statorassemblies (not shown) against a torque tube (not shown) in a knownmanner. The plurality of cylinders and associated pistons are arrangedradially in a substantially circular manner about the brake assembly 70,as is known.

The brake assembly 70 includes a brake inlet port 86. In this embodimentof the present invention, the brake inlet port 86 is not located at thetop of brake assembly 70. Instead, the brake inlet port 86 is located ata central location within the circular arrangement of cylinders so thatthe brake inlet port 86 is substantially equidistant from the cylinders.The brake inlet port 86 is coupled to a brake system (not shown) forreceiving brake hydraulic fluid for distribution to the plurality ofbrake cylinders.

Manifold sections 88 are provided for coupling the brake inlet port 86to each of the cylinders. Each manifold section 88 is substantially thesame length and has substantially the same volume. Each manifold section88 should be as short and straight as practicable to minimize hydrauliclosses and reduce time delays in filling the cylinders with hydraulicfluid. As can be seen in FIG. 5, the manifold sections 88 extendradially outward from the brake inlet port 86 to the plurality ofcylinders.

The brake assembly 70 achieves substantially coincident pistonapplication as follows. When the brakes are applied, hydraulic fluid issupplied to the brake inlet port 86. Hydraulic fluid flows from thebrake inlet port 86 through the manifold sections 88 to the plurality ofcylinders. Because the manifold sections 88 are substantially the samesize, hydraulic fluid is supplied to each of the cylinders atsubstantially the same time after the hydraulic fluid is supplied to thebrake inlet port 86.

FIGS. 6A-6D are schematic diagrams of other embodiments of a brakeassembly 90 according to the present invention; each of which uses bothparallel and series fluid supply to brake cylinders. In each instance, abrake assembly 90 has a plurality of cylinders 92, 94, 96, 98, 100, 102,and 104. Each of the cylinders is associated with a brake piston (notshown) for pressing against a pressure plate (not shown) to clamp brakerotor and stator assemblies (not shown) against a torque tube (notshown) in a known manner. As is known in the art, the plurality ofcylinders and pistons are arranged radially in a circular manner aboutthe brake assembly 90 for providing even clamping pressure. Thecylinders 92 and 104 are preferably located near a top region of thebrake assembly 90 that is near a brake inlet port 106, and the cylinder98 is preferably located near a bottom region of the brake assembly 90that is farther away from the brake inlet port 106. The brake assembly90 includes manifold sections 108 extending between adjacent cylinders.The brake inlet port is suitably located at the top region of the brakeassembly 90, as is well known in the art, but the location of the brakeinlet port 106 may be anywhere on the brake assembly 90. The manifoldsections 108 couple the cylinders 92, 94, 96, 98, 100, 102, and 104 inseries fluid communication with the brake inlet port 106, as is alsoknown in the art.

However, with reference to FIG. 6A, in accordance with the presentinvention a parallel distribution manifold section 110 alsohydraulically couples the lowermost cylinder 98 to the brake inlet port106. The cylinders are thus coupled in parallel fluid communication.

The embodiment of the present invention shown in FIG. 6A reducesasymmetric clamping of brake assemblies known in the prior art byincorporating a parallel fluid flow path into a brake assembly having aseries flow path. The brake assembly 90 operates as follows. When thebrakes are applied, hydraulic fluid is initially supplied to the brakeinlet port 106. Hydraulic fluid flows from the brake inlet port 106through the manifold sections 108 to the cylinders 92 and 104, as iswell known in the art. In accordance with the present invention,hydraulic fluid also flows through the parallel distribution manifoldsection 110 to the cylinder 98. The cylinders 92, 104, and 98 thereforefill with hydraulic fluid at substantially the same time. Therefore, thepistons (not shown) associated with the cylinders 92 and 104 locatednear the top region of the brake assembly 90 actuate substantiallycoincident with the piston (not shown) associated with the cylinder 98located near the bottom region of the brake assembly 90. It has beenshown during testing that pressure equalization of cylinders in responseto a step input occurred in 25% less time than the pressure equalizationtime for known brakes having only a series-connected manifold. Thisrepresents a major improvement over known brake assemblies that fillcylinders and actuate pistons solely in series. It will be appreciatedthat the brake assemblies 30 and 70 described above will provide an evenmore pronounced improvement over known brake assemblies that fillcylinders and actuate pistons solely in series.

The brake assembly 90 further reduces asymmetric brake clamping overbrake assemblies known in the art. The cylinders 94 and 102 fill withhydraulic fluid after the cylinders 92 and 104 fill with hydraulicfluid, as is known. However, the cylinders 96 and 100 fill withhydraulic fluid after the cylinder 98 fills with hydraulic fluid.Because the cylinder 98 fills with hydraulic fluid at substantially thesame time as the cylinders 92 and 104 fill with hydraulic fluid, thecylinders 94 and 102 fill at substantially the same time as thecylinders 96 and 100. Thus, the brake assembly 90 greatly reducesasymmetry in brake clamping over asymmetric brake clamping inherent inbrake assemblies known in the prior art.

In the arrangement shown in FIG. 6A, the preferred routing for theparallel distribution manifold section 110 is from the inlet port 106 toan oppositely disposed brake cylinder 98. However, the brakeconstruction may lend itself to a different routing for the paralleldistribution manifold section while still achieving advantages of morenearly coincident and balanced brake application. For example, asrepresented by broken line 112 in FIG. 6A, the routing may be from theinlet port 106 to a series manifold segment 108, preferably at theopposite side of the brake assembly from the inlet port. Anotherpossibility, represented by line 114 in FIG. 6A, is routing the paralleldistribution manifold section from a series manifold segment 108 nearthe inlet port 106 to an oppositely disposed brake cylinder 98; or, asrepresented by line 116 in FIG. 6A, from a series segment 108 near theinlet port 106 to a generally oppositely disposed segment 108. Dependingon the number and positions of the brake cylinders, these routings mayachieve improved results as compared to a system having only seriesconnected cylinders or, for example, a system having some paralleldistribution but with fluid paths of unequal lengths.

Similarly, with reference to FIG. 6B, the parallel distribution manifoldsection 110′ can have a first segment 118 extending from the inlet port106 which branches to other segments 120 and 122 to distribute hydraulicfluid to series manifold sections 108 at generally opposite sides of thebrake assembly, with or without an additional segment 124 extending tocylinder 98 or a segment 108 at the opposite side of the assembly frominlet port 106. As seen in FIG. 6C, the branches 120, 122 from thesegment 118 may extend directly to brake cylinders at opposite sides ofthe brake assembly, such as cylinders 94 and 102, with segment 124extending to cylinder 98 at the bottom. For the seven cylinderarrangement illustrated, it should be noted that three of the cylinders(94, 98, and 102) are fed directly from the inlet by way of the parallelmanifold segments, in addition to being fed by the series manifoldsections 108 from adjacent cylinders, and two cylinders (92 and 104) arefed directly from the inlet port by way of the series manifold sections108 extending from the inlet port, as well as by the series manifoldsections 108 from cylinders 94 and 102 which are fed by the branches120, 122. Two of the cylinders (96 and 100) are fed by series manifoldsections 108 from adjacent cylinders, but each of the adjacent seriesconnected cylinders is fed directly from the inlet port. Thus, a morenearly coincident application of braking force is achieved.

Another arrangement is illustrated in FIG. 6D where the segments 126,128, 130, and 132 extend from a series manifold section 108 close to theinlet 106 to other sections 108 located approximately equidistant for auniform and nearly coincident application of braking force.

While the preferred embodiment of the invention has been illustrated anddescribed, it will be appreciated that various changes can be madetherein without departing from the spirit and scope of the invention.For example, a parallel distribution manifold may be incorporated as aretrofit into a conventional brake assembly having cylinders connectedin series, rather than filling sequentially through series connections.Accordingly, the invention is not limited except as by the appendedclaims.

What is claimed is:
 1. A brake assembly comprising: a plurality ofcylinders for actuating a corresponding plurality of pistons, includingat least a first cylinder, a second cylinder, and a third cylinder foractuating corresponding pistons, the cylinders being arranged in asubstantially circular manner; a brake inlet port for receiving fluidfrom a fluid reservoir, the brake inlet port being located at a centrallocation within the circular arrangement of the cylinders so that thebrake inlet port is substantially equidistant from the cylinders andwhen fluid enters the brake inlet port, the fluid enters the brake inletport at the central location equidistant from the cylinders; a fluiddistribution manifold connected in fluid communication with the brakeinlet port and the first, second, and third cylinders, the fluiddistribution manifold connecting the first, second, and third cylindersin parallel fluid flow; and the fluid distribution manifold having afirst fluid distribution manifold section coupled between the brakeinlet port and the first cylinder, a second fluid distribution manifoldsection coupled between the brake inlet port and the second cylinder,and a third fluid distribution manifold section coupled between thebrake inlet port and the third cylinder, the first, second, and thirdfluid distribution manifold sections having first uniform lengths andvolumes, defining first, second and third fluid passages of equal lengthfrom the brake inlet port to the first, second and third cylinders,respectively, the first, second, and third cylinders actuating theircorresponding pistons at a first substantially uniform time interval. 2.The brake assembly of claim 1, wherein the brake inlet port is disposeda uniform distance from each of the cylinders, and the first, second,and third fluid distribution manifold sections are disposed radiallyoutward from the brake inlet port.
 3. The brake assembly according toclaim 1, wherein a flow restrictor is provided in each of the first,second, and third fluid distribution manifold sections.
 4. The brakeassembly according to claim 1 further comprising: a second fluiddistribution manifold connected in fluid communication with the brakeinlet port and the first, second, and third cylinders, the second fluiddistribution manifold connecting the first, second, and third cylindersin series fluid flow.
 5. A brake assembly having a plurality of brakefluid actuated pistons, the brake assembly comprising: a plurality ofcylinders for actuating a corresponding plurality of pistons, includingat least a first cylinder, a second cylinder, and a third cylinder foractuating corresponding pistons, the cylinders being arranged in asubstantially circular manner; a brake inlet port for receiving brakefluid from a fluid reservoir, the brake inlet port being disposed anequalized distance from each of the cylinders at a central locationwithin the circular arrangement of the cylinders and when fluid entersthe brake inlet port, the fluid enters the brake inlet port at thecentral location equidistant from the cylinders; and a plurality ofmanifolds, each of the manifolds coupling the brake inlet port to anassociated cylinder, each of the manifolds having an equalized lengthand an equalized volume such that the manifolds form fluid passages ofequal length from the inlet port to the cylinders and each of thecylinders actuates its corresponding piston at a first time interval. 6.The brake assembly of claim 5, wherein the plurality of manifolds aredisposed radially relative to the brake inlet port.
 7. A brake assemblycomprising: a brake inlet port for receiving fluid from a fluidreservoir; a fluid distribution manifold connected in fluidcommunication with the brake inlet port; a first cylinder for actuatinga first brake piston and connected in fluid communication to a firstsupply segment of the fluid distribution manifold to define a firstfluid path distance from the brake inlet port; a second cylinder foractuating a second brake piston and connected in fluid communication toa second supply segment of the fluid distribution manifold to define asecond fluid path distance from the brake inlet port that is greaterthan the first fluid path distance, the first and second supply segmentscoupling the first and second cylinders in series fluid communication;wherein the fluid distribution manifold includes a distribution segmentcoupling the first and second cylinders in parallel fluid communicationto equalize supply of fluid to the first and second cylinders; and aflow restrictor is provided within the distribution segment of thedistribution manifold coupling the first and second cylinders inparallel fluid communication, the flow restrictor reducing an effectivediameter of the distribution segment of the distribution manifold by apredetermined amount.
 8. The brake assembly according to claim 7,wherein the second cylinder is positioned substantially 180 degrees fromthe brake inlet port and the distribution segment of the distributionmanifold coupling the first and second cylinders in parallel fluidcommunication extends between the brake inlet port and the secondcylinder.
 9. A method of concurrently actuating a plurality of brakefluid actuated pistons of a brake assembly, the brake assembly having abrake inlet port, the brake assembly having at least a first cylinderfor actuating the first piston, a second cylinder for actuating thesecond piston, and a third cylinder for actuating the third piston, thefirst cylinder being coupled in fluid communication with the brake inletport through a first fluid path, the second cylinder being coupled influid communication with the brake inlet port through a second fluidpath, and the third cylinder being coupled in fluid communication withthe brake inlet port through a third fluid path, the method comprising:supplying brake fluid to a brake inlet port; applying brake fluid fromthe brake inlet port to a first cylinder through a first manifoldsection and a first flow restrictor provided in the first manifoldsection to reduce an effective diameter of the first manifold section bya first predetermined amount, for actuating a first piston; applyingbrake fluid from the brake inlet port to a second cylinder through asecond manifold section and a second flow restrictor provided in thesecond manifold section to reduce an effective diameter of the secondmanifold section by a second predetermined amount, for actuating asecond piston; and concurrently applying brake fluid from the brakeinlet port to a third cylinder through a third manifold section and athird flow restrictor provided in the third manifold section to reducean effective diameter of the third manifold section by a thirdpredetermined amount, in parallel fluid communication with brake fluidapplied to the first and second cylinders, the first, second, and thirdpredetermined amounts being selected such that the first, second, andthird pistons actuate at an equalized time interval.
 10. The methodaccording to claim 9, further comprising: restricting the flow of brakefluid from the brake inlet port to the third cylinder.
 11. A brakeassembly comprising: a plurality of cylinders for actuating acorresponding plurality of pistons, including at least a first cylinder,a second cylinder, and a third cylinder for actuating correspondingpistons, the cylinders being arranged in a substantially circularmanner; a brake inlet port for receiving fluid from a fluid reservoir,the brake inlet port being positioned at a central location within thecircular arrangement of the cylinders and when fluid enters the brakeinlet port, the fluid enters the brake inlet port at the centrallocation with fluid paths of equal distance from the inlet ports to thecylinders; a fluid distribution manifold connected in fluidcommunication with the brake inlet port and the first, second, and thirdcylinders, the fluid distribution manifold connecting the first, second,and third cylinders in parallel fluid flow; and the fluid distributionmanifold having a first fluid distribution manifold section coupledbetween the brake inlet port and the first cylinder, a second fluiddistribution manifold section coupled between the brake inlet port andthe second cylinder, and a third fluid distribution manifold sectioncoupled between the brake inlet port and the third cylinder, the first,second and third fluid distribution manifold sections havingsubstantially uniform volumes, the first, second and third cylindersactuating their corresponding pistons at a first substantially uniformtime interval.
 12. A brake assembly comprising: a first brake cylindercomponent; a second brake cylinder component; a third brake cylindercomponent; series manifold distribution section components connectingthe first, second and third brake cylinder components in series; a brakeinlet port for receiving fluid from a fluid reservoir and for supplyingthe fluid to the series connected first, second and third brake cylindercomponents; and a parallel distribution manifold section extendingbetween components of the brake assembly and supplying a paralleldistribution path of the fluid to the brake cylinders.
 13. The brakeassembly defined in claim 12, in which the parallel distribution sectionextends from the brake inlet port to one of the brake cylindercomponents.
 14. The brake assembly defined in claim 12, in which theparallel distribution section extends from the brake inlet port to oneof the series manifold section components.
 15. The brake assemblydefined in claim 12, in which the parallel distribution section extendsfrom one of the series manifold section components near the brake inletport to one of the brake cylinder components.
 16. The brake assemblydefined in claim 12, in which the parallel distribution section extendsfrom the brake inlet port to one of the series manifold sectioncomponents.
 17. The brake assembly defined in claim 12, in which thebrake cylinder components are arranged in a substantially circularmanner, and the parallel distribution manifold section extends betweencomponents at opposite sides of the brake assembly.
 18. The brakeassembly defined in claim 17, in which the parallel distributionmanifold section is branched and connects at least three locations ofthe substantially circularly arranged cylinder components.
 19. The brakeassembly defined in claim 18, in which the three locations include thebrake inlet port and at least one of the cylinder components.
 20. Thebrake assembly defined in claim 18, in which the three locations includethe brake inlet port and at least one of the series manifold sectioncomponents.
 21. The brake assembly defined in claim 17, in which theparallel distribution manifold section includes a substantially straightconduit extending generally diametrally of the substantially circularlyarranged cylinder components and series manifold section components.